C YTOGENETICS L ABORATORY , H OSPITAL FOR S ICK C HILDREN
G ENOMIC M ICROARRAY WITH SNP A NALYSIS
Genomic microarray analysis is the latest technology in chromosome testing
that can find small pieces of missing or extra chromosome (genetic) material.
These missing or extra pieces are known as copy number variants (CNV). Microarray can detect small CNVs that were not detectable by previous technologies, such as a karyotype. CNVs may help us to understand why an individual
has health problems (e.g. heart defect) or developmental delay (e.g. learning
disabilities, mental handicap). Recent studies have shown that approximately
10-20% of individuals with unexplained developmental delay or multiple congenital anomalies will have a CNV considered to be clinically relevant.
This SNP microarray platform will also detect absence of heterozygosity (AOH).
AOH affecting multiple chromosomes suggests these regions are identical by
descent. This information is included in the report for clinical interpretation by
the referring clinician. AOH restricted to one chromosome may be suggestive of
uniparental disomy (UPD). However, this assay is not designed to offer
comprehensive UPD analysis. Standard molecular tests should be ordered if a
disorder associated with UPD is suspected.
C HROMOSOMES & M ICROARRAY
For More Information
Information regarding requisitions and sample requirements
can
be
found
at:
www.sickkids.ca/cytogenetics
For more detailed information
on microarray technology and
its uses, see the pamphlet
published by Unique:
www.rarechromo.org/forum/
DisordersLeaflets.asp
To locate a genetics center
near you, please visit the Canadian Association of Genetic
Counsellors website at
www.cagc-accg.ca or the
National Society of Genetic
Counsellors website at
www.nsgc.org
The human body is made up of millions of tiny cells. Inside each cell is a set of chromosomes which contain our genes. A person’s genes will determine how they will grow
and develop, both physically and intellectually. Microarray can detect missing or extra
genetic information that can cause health or developmental problems. The type of problems will depend on the function of the missing or extra genes. This test can also find
missing or extra genetic information that may not cause health problems, because no
important genetic information is affected.
P OTENTIAL O UTCOMES & I NTERPRETATION
OF
T EST R ESULTS
R ESULT
I NTERPRETATION
Normal
No abnormality identified. The cause of the individual’s
health and/or developmental problems remains unexplained.
Pathogenic
variant found
A CNV that is associated with a specific pattern of health
and/or developmental problems is identified. An additional
blood sample from the child and parents may be recommended to investigate the origin of the CNV.
Genetic assessment/counseling will be recommended.
Variant of
unknown
significance
found
A CNV of unclear significance is identified. This variant may
or may not be related to the child’s health and/or developmental problems. Testing of the child’s mother and father
may be recommended to assist with the interpretation.
Genetic assessment/counseling may be recommended.
Unexpected
finding
Although this is unlikely, CNVs may be identified that are
unrelated to the health/developmental problems in the child,
but could possibly cause other health problems in the future.
Genetic assessment/counseling will be recommended.
Absence of
AOH of multiple chromosome regions suspected to be identical by descent will be reported for clinical interpretation by
the referring physician. The laboratory does not use this
data for clinical interpretations. AOH results suggestive of
UPD of a clinically significant region will require follow-up by
molecular tests designed specifically to detect UPD.
Heterozygosity
This document was developed by The Division of Clinical and Metabolic Genetics and The Division of
Molecular Genetics, Department of Paediatric Laboratory Medicine, The Hospital for Sick Children
1. C u r r e n t
microarray
technologies will not detect
single gene disorders or
balanced
chromosome
rearrangements.
2. A normal microarray result
does not rule out the possibility
of a genetic cause for an
individual’s
health or
developmental concerns.
3. Test results should be
interpreted in the context of
clinical findings, family history
and other laboratory data.
4. This test was developed
and
its
performance
characteristics validated by the
Cytogenetics Laboratory at the
Hospital for Sick Children. It
has not been cleared or
approved by the U.S. Food and
Drug Administration. The FDA
has determined that such
clearance or approval is not
necessary. This test is used for
clinical purposes.
OCG-1718B-01